IMHO the answer is NO because it will be harder to filter any conducted emissions from the device(s) being powered, so there is more chance of interference with avionics.
A floating output seems to be easier to filter.
What does the STC say about installing that thingy ?
This Q is not about a specific product.
Also would a USB power outlet need an STC – except for marketing purposes?
Peter wrote:
would a USB power outlet need an STC
That’s a good question, and since it is hard-wired to the electrical bus, as opposed to simply plugged into the cigar lighter receptacle, some might consider it a “change to the basic design of the electrical system”, whilst others not.
That line of reasoning would mean that any addition to anything would be a “basic change” which would mean that you would need an STC for
which is clearly not the case.
That’s correct, but that doesn’t mean that I share that line of reasoning …
And it clearly IS the case in the eyes of MANY FAA certified A&Ps & IAs !
If an A&P/IA says one cannot fit a backup voltmeter (e.g.) then I would find another A&P/IA, because that is a completely outrageous interpretation of the wording. Common, though, I agree…. but a lot of people in the engineering business have not read the regs since they left the course.
Peter – That FAA Policy document is an absolute jewel for more reasons than one !
Check out what it considers to be a “Minor” electrical alteration :
To install an electronically-driven attitude indicator as a minor alteration, the above conditions
and the following additional regulations must be met:
1. The electronically-driven attitude indicator must fit into the existing location of the
vacuum-driven attitude indicator and be properly set to indicate level flight. The existing
airspeed, altitude, and turn/bank indicators must remain in their originally certificated or
basic “T” locations. If any additional openings or modifications to the instrument panel
are required to install the electronic instrument, the following requirements must be met:
i. The instrument panel cannot be part of the aircraft primary structure; or
ii. If the instrument panel is part of the aircraft primary structure, the aircraft
manufacturer’s instructions must include instrument panel modification instructions.
2. The electronically-driven attitude indicator requires only minor changes to the existing
electrical and vacuum connections to the aircraft, per part 43.
3. The electronically-driven attitude indicator must be powered from a new, dedicated circuit
breaker (or other appropriate circuit protection device), and it must be powered by a
standby (backup) power source
Clearly, based on the above document excerpt, adding a simple device to the bus is considered "Minor " !
Conclusion
Based on this policy, vacuum-driven attitude indicators can be directly replaced with
electronically-driven attitude indicators to enhance small aircraft safety. These alterations can be
approved through the Amended Type Certificate, Supplemental Type Certificate, Amended
Supplemental Type Certificate, Field Approval (Form 337), or Minor Alteration processes, as
appropriate. However, the intent of this policy is to communicate that most replacements can
likely be done as minor changes
Any views on the original grounding question?
